Electric fence



Nov. 5, 1940. c. E. PETERS 2,220,687

' ELECTRIC FENCE Filed Aug. a, 1958 INVENI'OR. CARL E. PETERS ATTORNEY.

Patented Nov. 5, 1940 UNITED STATES PATENT OFFICE ELECTRIC FENCE Application August 8, 1938, Serial No. 223,597

2 Claims.

This invention relates to means for electrifying a fence with rectified alternating current. Increased use is being made of an electrified wire as a fence for protecting enclosures. With such a fence, it is only necessary to use a single electrified wire supported by suitable insulators on the fence posts instead of the usual fence composed of many wires. The use of a single electrified wire considerably reduces the cost of the a fence and it is particularly useful where large aoreages are involved.

The high voltage for the electrified fence is usually obtained from a high voltage supply energized from either an alternating or direct current source of supply. This invention concerns primarily the type of high voltage supply which utilizes an induction coil provided with an interrupter in the primary circuit and energized from a low voltage direct current source of supply. Such a device may be used in connection with batteries or a rectified alternating current. In order that persons or cattle will not be injured by contact with the electric fence, it has been found necessary to maintain the high voltage a current in the wire for only short intervals of time. It has been found that ten to fifteen of these impulses per second is suflicient for the protective purposes of the fence and yet not enough to prevent a person who has contacted a the fence from disengaging himself.

It is important that provision be made to insure that a dangerous current cannot be sent into the fence if the interrupter contacts should stick. If a battery is used as the source of supply, the high voltage output of the induction coil would be zero even though the interrupter contacts in the primary circuit should freeze, since the output of a battery is pure D. C. If, however, a rectifier is used instead of a battery, it is possible that a dangerous output to the fence might result from the induction of a high voltage in the transformer or induction coil secondary because of the A. C. ripple in the rectifier. The reasons for such a result will appear from the description which follows.

It is an object of this invention to provide a safe means for supplying high voltage fence units with a rectified alternating current. Further ob- Jects and advantages will appear from the acu oompanying drawing and following detailed description.

For the purpose of illustrating one embodiment of my invention, I will now describe my invention as shown in the accompanying drawing.

a Fig. 1 is a schematic diagram or a high voltage device provided by my invention is shown as a part of the interrupter and induction coil unit.

Referring now to the drawing in which the same numerals are used to indicate the same or similar parts, 3 is a suitable housing or com- 10 partment containing the high voltage supply mechanism. 5 and 1 are input terminals which are to be supplied from a direct current source of approximately 6 to 12 volts. 9 is an induction coil or high voltage transformer with its sec- 15 ondary connected to the high voltage supply terminals H and I3, one of which is grounded and the other of which is connected to the electrified wire of the fence. I5 is the primary of the induction coil or transformer. I1 is an interrupter which may be any one of many kinds customarily employed to intermittently make and break a primary circuit. For electric fence operation, an' interrupter may be so designed that it will close for approximately .1 of a second every of a second. It is obvious, of course, that different periods of contact and longer or shorter times between periods of contact may be used as conditions require. I9 is the electrified wire fence,

2| the insulators used to support the wire, and 3 23 the fence post. 24 is a ground connection.

If instead of a battery, an ordinary rectifier is used to supply the posts 5 and l, the device will operate reasonably satisfactorily until the interrupter contacts stick. At times, however, the interrupter i! may stick or freeze. When this occurs, an appreciable ripple will appear in the output of the rectifier since it will be quite overloaded owing to the low resistance of the primary of the induction coil. Because of the transformer action of induction coil 9, this ripple will cause a high voltage alternating current to appear across the fence. This would be objectionable for it would be continuous and any object coming in contact with the fence could not withdraw from the wire and might be seriously injured. I have provided a means which may be used in connection with a rectifier, however, which will obviate the possibility of such a dangerous result. In the embodiment shown in Fig. 1, I incorporate this means with a rectifying means to form a rectifying unit. My rectifying unit may comprise a box or housing 25 enclosing a step-down transformer 21 whose primary is brought out through terminals 29 and 3| which may be connected to the usual alternating current source of supply. The secondary of the transformer 33 is connected to a dry disk rectifying means 35. This rectifying means and the secondary of the transformer are chosen to obtain the proper voltage values on the output terminals 31 and 39 of the direct current supply unit. A series resistor M of 50 ohms is connected as shown in series with the output of the rectifying means and a 2,000 microfarad condenser 43 is connected across theoutput as shown. With such a direct current supply, if the c-on-= tacts of the interrupter should stick or freeze, the resistor 3! will maintain the current output of the rectifier at or below its normal flow so that no appreciable A. C. ripple will appear in the output of the rectifier. This in turn will prevent any high voltage alternating current from appearing on, the fence terminals when the interrupter contacts stick. The resistor alone, however, while providing a means for controlling the short circuited output of the rectifier, would not allow suificient current to pass from the rectifier during normal closure of the interrupter I! to obtain a high voltage discharge from the induction coil. To provide for this normal operation, I insert the condenser 43. During normal operation; while the interrupter is open, current will flow from the rectifier through the resistor and charge the 2,000 microfarad condenser. When the contacts close, this current which was stored up in the condenser will fiow through the primary of the induction coil until the interrupter breaks the circuit and induces a high voltage in the secondary of the high voltage transformer. With the interrupter open again, the condenser will again be charged for the next closing of the interrupter.

Fig. 2 shows the same protective current limiting means, shown in Fig. 1 in the rectifier unit, included as a part of the induction coil and interrupter unit. A manufacturer could sell a high voltage and interrupter unit as shown in Fig. 2

for .use with either a battery or rectifier. When a battery is used to supply energy forthe induction coil and interrupter fence unit, the resistor 4| and condenser 43 will prevent instantaneous high amperage discharges from the battery to the primary of the induction coil each time the interrupter makes contact and instead will cause the induction coil to draw its current from the condenser which may be charged rather slowly. The operation of this unit will be much the same as explained above in connection with Fig. 1. If a rectifier unit is substituted for the battery as input current supply for the induction coil and interrupter fence unit (Fig. 2), the same protection will be afforded to eliminate dangerously high voltage on the fence as has been discussed in connection with the scheme shown in Fig. 1.

It is obvious that the rectifier, protective resistor, and condenser and the interrupter and induction coil could be made into a single unit if desired. The resistor and condenser included in the induction coil and interrupter unit insure against dangerous results from a unit which has been bought as a battery unit and then changed over to an ordinary rectifier supply. Thus while the.high voltage unit shown in Fig. 1 would be safe with only a battery or special rectifier, the high voltage unit shown in Fig. 2 could be used with any battery or rectifier without dangerous results.

The difference in operation between the normal rectifier and the D. C. voltage supply provided in my invention can be illustrated by the following test: A 500 ohm non-inductive resistor was substituted for the electric fence and with -an ordinary rectifier supplying the direct current for the terminals of thehigh voltage supply unit of Fig. 1. With the interrupter contacts held shut, a reading of volts was obtained across the 500 ohm resistor. The current supplied the primary of the high voltage transformer was amperes. The same procedure was followed with the D. C. supply unit of Fig. 1 employing the safety means provided by my invention and the same rectifying means, and the voltage across the 500 ohm resistor was found to be only .7 of a volt with the interrupter held closed and the pulsating direct current only .13

ampere.

It can be seen, therefore, that my device dispenses with the necessity for high priced filters and, at the same time, insures that a continuous injurious voltage cannot appear across a fence even though the interrupter contacts should stick.

While I have illustrated and described one form of device embodying my invention, it is obvious that various omissions, modifications,

substitutions, and additions may be made in the device described without departing from the spirit and scope of the invention which I have defined in the appended claims.

I claim:

1. A protective electric fence comprising a conductor insulated from the ground, an induction coil provided with a high and low voltage winding and having one terminal of its high voltage winding connected to said conductor, an interrupter adapted to intermittently open and close a circuit, in series with one side of the low voltage winding of the induction coil, a condenser between the other side of the low voltage winding and the side. of the interrupter away from the low voltage winding, 8. rectifier for converting alternating to direct current,-conductors between each side of the rectifier means and the corresponding side of the condenser, and a resistor in series with one of said conductors, the. size of the induction coil being such that the current required for operation thereof is more than the normal current output of the rectifier, the resistor being of a size whereby the current from the rectifying means is limited to its normal value and one which will not produce an alternating current ripple in the rectifier output, the condenser being of a size sufficient to store enough current from the normal output of the rectifier during the open periods of the interrupter to supply the current necessary for the operation of the induction coil during the closed periods of the interrupter.

2. In a device for supplying an intermittent high voltage to a fence wire, an induction coil provided with a high and low voltage Winding and having one terminal of its high voltage winding connected to said fence, an interrupter adapted to intermittently open and close the circuit in series with one side of the low voltage winding of the induction coil, a condenser be tween the other side of the lowvoltage winding and the side of the interrupter away from the low voltage winding, a dry disc rectifier for supplying low voltage direct current to the condenser, a resistor between the rectifier and the condenser, the size of the induction coil being such that the current required for the operation thereof when the interrupter is closed is more than the normal current output of the rectifier, the resistor being of a. size whereby the current from the dry disc rectifier is limited to its normal value and one which will not produce an alternating current ripple in the rectifier output even though the interrupter be closed, the condenser being of a size suflicient to store enough current from the normal output of the rectifier during the open periods of the interrupter to supply the current necessary for the operation of the induction coil during the closed periods of the interrupter.

CARL E. PETERS. 

